This invention relates generally to water wells and more particularly to a method and apparatus for enhancing development of wells and rehabilitating existing wells that have lost capacity.
Water wells and other wells that have been in production for a considerable length of time often lose capacity for a variety of reasons. One of the main reasons is that the well screen and/or the filter pack and surrounding formation fractures tend to become clogged with sand, clay, bacteria and other growths and materials that build up and impede entry of liquid into the well.
Various techniques have been used to restore lost capacity, including chemical injection, mechanical agitation, sonic energy application and electrical stimulation. None of these approaches has been entirely satisfactory. Chemical cleaning methods have typically involved pumping or gravity feeding chemicals into the well. The chemicals follow the path of least resistance which is usually not where the clogging takes place. Thus, conventional chemical injection has not been wholly effective.
Mechanical agitation of the well and screen from the inside dislodges scale and other built up material from the inside of the well. However, it does not affect the filter pack surrounding the well or the fractures in the surrounding formation, so deposit laden areas located outside of the well remain as a source of plugging. The use of sonic energy and electrical energy has been attempted but has not achieved widespread acceptance due largely to cost problems and lack of effectiveness.
Accordingly, a need remains for an effective way to remove material that clogs wells, well screens, and the surrounding filter pack and fractures, both in newly developed wells and in existing wells that have lost production capacity. It is the primary goal of the present invention to met that need.
In accordance with the invention, gas is applied under pressure in a sidewardly direction in the production zone of a well in controlled bursts. The pressurized gas creates shock waves that cause water and gas to flow outwardly and break down materials that have built up on the screen and also in the surrounding filter pack and formation fractures. At the end of each burst, a flushing effect ensues to draw the loosen particulate material into the well from the surrounding formation. These particles are then removed by a submersible pump or air lift assembly that forces water from the well to the surface. The gas bursts are generated throughout the entirety of the production zone of the well in order to thoroughly clean it and thereby significantly enhance its capacity.
Preferably, the gas bursts are controlled by a relief valve which is positioned down in the well and set to open when subjected to a selected pressure. When the relief valve opens, the gas is discharged sidewardly through side ports or through an open annulus so that the gas is applied directly to the well screen or louvers in a manner to maximize the dislodging of materials that plug the well. Mechanical agitation with agitating discs may be used along with the gas bursts. Chemicals may also be used and are particularly effective because they are carried by the gas outwardly into the formation where they can attack the deposits located there.